Soda inclusive glasses are known in the art. For example, see U.S. Pat. No. 5,214,008, which is hereby incorporated herein by reference.
Soda lime silica glass, for example, is used for architectural glass, automotive windshields, and the like. The aforesaid '008 patent discloses one type of soda lime silica glass known in the art.
Unfortunately, conventional soda inclusive glasses are susceptible to environmental corrosion which occurs when sodium (Na) diffuses from or leaves the glass interior. This sodium, upon reaching the surface of the glass, may react with water to produce visible stains or smears (e.g. stains of sodium hydroxide) on the glass surface. Such glasses are also susceptible to retaining water on their surfaces in many different environments, including when used as automotive windows (e.g. backlites, side windows, and/or windshields). These glasses are also susceptible to fogging up on the interior surface thereof in automotive and other environments.
In view of the above, it is apparent that there exists a need in the art to prevent and/or minimize visible stains/corrosion on soda inclusive coated glass surfaces. There also exists a need in the art to provide a strong protective coating on window substrates. Other needs in the art include the need for a coating on glass that reduces the coated article's susceptibility to fogging up in automotive and other environments, and the need for a coated glass article that can repel water and/or dirt.
It is known to provide diamond like carbon (DLC) coatings on glass. U.S. Pat. No. 5,637,353, for example, states that DLC may be applied on glass. The '353 patent teaches that because there is a bonding problem between glass and that type of DLC, an intermediate layer is provided therebetween. Moreover, the '353 patent does not disclose or mention the highly tetrahedral amorphous type of DLC used in many embodiments set forth below. The DLC of the '353 patent would not be an efficient corrosion minimizer on glass in many instances due to its low density (likely less than 2.0 gm/cm.sup.3). Still further, the DLC of the '353 patent is deposited in a less than efficient manner for certain embodiments of this invention.
It is known that many glass substrates have small cracks defined in their surface. The stress needed to crack glass typically decreases with increasing exposure to water. When water enters such a crack, it causes interatomic bonds at the tip of the crack to rupture. This weakens glass. Water can accelerate the rate of crack growth more than a thousand times by attacking the structure of the glass at the root or tip of the crack. Strength of glass is in part controlled by the growth of cracks that penetrate the glass. Water, in these cracks, reacts with glass and causes it to crack more easily as described in "The Fracturing of Glass," by T. A. Michalske and Bruce C. Bunker, hereby incorporated herein by reference. Water molecules cause a concerted chemical reaction in which a silicon-oxygen bond (of the glass) at the crack tip and on oxygen-hydrogen bond in the water molecule are both cleaved, producing two silanol groups. The length of the crack thus increases by one bond rupture, thereby weakening the glass. Reaction with water lowers the energy needed to break the silicon-oxygen bonds by a factor of about 20, and so the bond-rupture allows glass cracks to grow faster.
Thus, there also exists a need in the art for preventing water from reaching silicon-oxygen bonds at tips of cracks in a glass substrate, so as to strengthen the glass.
It is a purpose of different embodiments of this invention to fulfill any or all of the above described needs in the art, and/or other needs which will become apparent to the skilled artisan once given the following disclosure.